The mechanics of probability

if i'm counting cards in blackjack and at some point work out that the probability of the next card being dealt being a 10 or higher is 2/1, and the dealer suddenly reshuffles the deck, that probability evaporates (ask any card counter)...but why? what is going on here? reshuffling the deck doesn't alter which cards have been dealt so it doesn't alter the count that led to my 2/1 probability, so what then does it alter? is there some explanation that comes from quantum mechanics? does it have to do with wave functions?